The study conducted in Japan was published in the Journal of Functional Foods.​

Lactobacillus gasseri CP2305 is a “paraprobiotic” which is a heat-inactivated, enteric-colonising strain isolated from the stool samples of a healthy volunteer.

In the study, 49 male university students between the age of 18 and 22 years old who are also members of the Aoyama Gakuin University Ekiden Team (long distance relay race) were recruited.

They were then randomly divided into two groups, with one group consuming 200ml of placebo isotonic sports drink, while the intervention group took the same amount of sports drink containing CP2305 daily.

The experiment took place for 12 weeks when the athletes were training and competing in three national university championships, namely the Izumo All Japan University Ekiden, and the Hakone Ekiden.

They were also instructed to continue their daily diet and told to avoid other probiotics products. They were also required to record their daily running distance.

The physical and mental health of the athletes were then assessed using four sets of questionnaires, such as the Chalder Fatigue Scales (CFS), the Spielberger State-Trait-Anxiety Inventory (STAI), and Hospitality Anxiety and Depression Scale (HADS), before the start of the experiment and during the 6th​ and last week of the experiment.

Other tests include measurements of salivary cortisol and chromogranin A – a salivary stress marker. Analysis of their fecal microbiota and gene expression also took place.

Less stressful ​

The study found that CP2305 intake could reduce post-exercise anxiety levels as seen in the questionnaire and test results in the intervention group.

It found that fatigue and anxiety scores as seen from CFS, STAI, and HADS questionnaire had decreased, while that of the placebo remained at about the same levels after six weeks of the test.

“Usually, the STAI-trait score does not change in a short period of time; however, the CP2305 group had a significant reduction in STAI-trait scores. This may have been influenced by the effective relief of anxiety in the CP2305 group​,”​ the researchers said.

The study also showed that the amount of salivary stress marker – chromogranin A – had also significantly decreased in the intervention group.

For instance, the chromogranin A levels dropped by 10 pmol/mg protein after six weeks for the intervention group, while that of the placebo group had slightly increased.

Increasing diversities of fecal microbiota​

Researcher also found that daily intake of CP2305 had increased the fecal microbiota diversity, especially in the amount of faecalibacterium.​

For example, the percentage of faecalibacterium ​had increased from 13.3 (± 7.2) to 18.6 (±11.1) after 12 weeks of the study, while that of the placebo group was between 12.7 (± 9.3) and 14.2 (± 8.0) during the start and end of the study.

The researchers added that the reduction of bifidobacterium ​was significantly prevented by the daily intake of CP2305 in the intervention group.

Different groups, different effects​

Comparing the results to a previous study of CP2305 on university medical students who also experience stress due to heavy academic demands, the researchers found that CP2305 exerted different impact on different groups of people.

In this case, CP2305 was more effective in relieving fatigue and anxiety in athletes than in medical students.

“Paraprobiotic CP2305 may be more effective in exerting beneficial effects on intense exercise-associated symptoms rather than on naturally-induced stresses,” the researchers said.​

“Interestingly, paraprobiotic CP2305 significantly reduced salivary concentrations of chromogranin A ​rather than cortisol ​(in the athletes); however, the latter was significantly suppressed in medical student,”​ the researchers said.

They concluded that the trial showed that daily CP2305 intake was effective in recovering from fatigue and in relieving anxiety and depressive mood during vigorous physical training.

However, they acknowledged that they could not detect any significant difference in physical performance between the intervention and placebo group.

“Since there are individual variations and variable factors for physical performance, further studies are required to elucidate the beneficial effects of paraprobiotic CP2305 on the physical performance of athletes,”​ they said.